Overdrive control system



` Patented May 13, 1941 2,241,631 y s ovxlzrmarvs coN'rnoL SYSTEM Edward M. Claytor, Anderson, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application November 23, 1938, Serial No. 241,917

4 claims. (C1. 74-290) This invention relates to overdrives for auto,- mobiles. The type of overdrive to which the present invention relates is a device which is located in the line of transmission between the change speed gear box and the driving wheels of the Vehicle. This overdrive includes a sun gear cooperating with a planet gear which in turn drives an internal gear. The internal gear, or the frame which supports it, is the gears react against the sun gears while they are transmitting power to the internal gear which operates the propeller shaft connected with the rear or driving wheels of the vehicle. Therefore, it has been found necessary to relieve the torque of the engine at the instant the sun gear latch is withdrawn from engagement with the hub of the sun gear. Heretofore the relieving of the torque of the engine is effected by grounding certain objections to the grounding of the ignition as conditions mayv arise whereby a sparking Cil impulse would be delivered to the wrong engine spark plug. To overcome this dliculty, I have provided a means for automatically interrupting the connection between the current source and the ignition apparatus so that the possibility of a miss-fire of the engine will be avoided.

Further objects and advantages of the presentA invention will beapparent from the following description, reference being had to the acdriven member .of the overdrive mechanism. 10 companying drawing wherein a preferred em- The driving member of the overdrive mechanism bodiment of the present invention is clearly is a shaft around which the sun gear may rotate shown.

unless it be otherwise fixed from rotating. In the drawing:

Around this same driving shaft there rotates a Fig. 1 is a view partly diagrammatic, partly ring carrying one or more of the planet gears. 15 structural showing a form of overdrive mecha- 'Ihe planet gear carrying ring is automatically nism equipped with the electrical control appaconnected with the driving shaft by a centrifratus which constitutes an .embodiment of the ugal latch. When the overdrive is operating, invention. the sun gear is latched in stationary position. Fig. 2 is a chart which shows the operation When it is desired to render the overdrive in- 2e of the apparatus shown in Fig. lunder different operative, the sun gear latch is withdrawn to conditions. Y permit the sun gear, the planet gears and the Referring to Fig. l, numeral I indicates the internal gear to rotate together.V Under these driving shaft of the overdrive mechanism. The conditions .the drive shaft drives the frame shaft I receives its power from the change speed which carries the internal gear through the 25 gear mechanism housed in a box which would interposition of a one-way clutch. be located between the overdrive mechanism and This invention has to do with electrically the engine clutch. The shaft I is provided with operated mechanism for controlling the sun external splines 2 which mesh with internal gear latch. The sun gear latch is spring pressed splines 3a of the ring 3 and with internal splines into a notch on the edge of the hub of the sun 3o 9a of the driving member of an over-running gear in order to hold the sun gear in stationary clutch 9. The external splines 2 mesh also with position. Whenit is desired to withdraw the internal splines 8a of a coupling member 8 to latch, current is sent from a storage battery or which the propeller shaft 8b may be attached. other/ current source into an electromagnet The splines 2 connect togetherthe members 3 which lifts the latch from disengagement with 35 and 9 as shown in Fig. 1, when it is desired to the sun gear. When the sun gear latch is being use the over-drive mechanism. When it is not disengaged from the hub of the sun gear, it will intended that the over-drive mechanism shall lmeet with resistance due to the fact that the be used for anyvconsider'able period of time, the engine is applying power to the rear wheels ofy over-drive may be entirely disconnected by movthe vehicle through the planet gears. The planet 40 ing the shaft I endwise towards the left so that its external splines 2 will engage the internal splines 8a of the member 8, thus connecting together the members 8 and 9 and leaving the member 3 free. The shaft I is sup-ported for axially movement at both ends. for the right hand end of the shaft I is not Y shown. At the left end of the shaft I it is pro'- vided with a reduced portion Ia having a sliding t within an axially alined recess 8c provided in the member 8;

The member 3 is connectible with the member 5 by means of aspeed responsive latch 4. Member 5 is the'planet gear ring supporting one or more planet gears 6. The planet gears 6, which are mounted upon rods 6a extending from the The support ring 5, mesh with sun gear II and with an internal gear -1a supported by a frame 1 which cooperates with the clutch rollers IIl which in turn cooperate with a driving clutch cam 9 to receive transmission of torque from the driving member at such times as the driving member 9 tends to rotate ahead of the member 1. However, when the hub of the sun gear II- is engaged by a sun gear latch I2 which drops into a notch I Ia of the hub of the sun gear as shown in Fig. l, then' the external gear 1a and hence its frame 1 are driven at a speed exceeding the speed 'of the clutch driving member 9. Under these conditions the member 1 will over-run the clutch driving member 9.

The sun gear latch I2 isurged downwardly into latching position by a spring I2a. conned between the head of the latch I2 and the base I6 of a latch operating solenoid. The solenoid which lifts the sun gear latch I2 comprises va solenoid armature I4 connected with the latch I2 by a rod I3. The solenoid includes two magnet coils I1 and I8 which are connected together at the point I18. `Coil I8 is grounded, and coil I1 is connected with the stationary contact I9 engageable by a movable contact 28 and xed to the end of a leaf spring member 2| which is grounded. To the solenoid armature I4 there is fixed a rod I5 which engages the blade 2I to separate the contact 28 from the contact I9 when the solenoid armature I4 is attracted upwardly to retract the latch I2 from the notch I Ia in the sun gear hub.

lThe terminal I.18 which is common to the solenoid magnet coils I1 and I8 is connected by Wire 22 with/rfi: source of current through a relay mechanism to be described later. The `coils I1 and I 8 act cumulatively to effect the attraction of the armature I4 upwardly to withdraw the latch I2 from the sun gear. Since the amount of magnetic flux required to maintain the solenoid I4 in attracted position is much less than that required to withdraw the latch I2 from the sun gear, the magnet coil I 1 is disabled by the opening of contacts 20 and I9 which is effected by the engagement of the rod I with the spring blade 2I.

If'he latch solenoid and the engine ignition are controlled by an assemblage of relays which will now be described. The relay assembly comprises two relays. One relay includes a magnet Winding the transmission of torque from the shaft I through the elements 2, 3, 4, l5, 8, 1 and 8. The element 1 is driven faster than the element I by the operation of the planetary gear 1. Hence the member 1 which constitutes the driven member of an overrunning clutch is driven at a rate faster than it can be driven by the driving member 9 of the overrunningclutch Hence the member 1 overruns the member 8.

When it is desired to dispense with the operation of the overdrive, the car driver will depress the switch S to cause the contact 30 to bridge the 25 and normally closed contacts 3I and 32 hereinafter referred to as the pair of contacts B. Contact 32 is connected by ignition switch 33 with a 'wire 34 leading to the engine ignition apparatus. Relay magnet 25 is connected With a current source such as a storage battery 26 which is grounded. Relay magnet coil 25 is connected with a pair or normally open contacts A comprising a contact 24 directly connected with Poil 25 and a contact 23 connected with the wire 22. Contacts A are parts of a second relay which contacts 28 and 29, thereby causing current to flow from the battery 26 through the relay coil 21. The excitation of relay coil 21 effects the attraction of an armature, not shown, which causes the pair of contacts A which are normally open to be closed,` thereby connecting the battery with the relay winding 25 and with the solenoid magnet windings I1 and I8. Winding I1 is of low resistance and produces the major portion of theiiuxrequired to attract the armature I4. Winding I8 is of higher resistance and will be ineffective, unaided by winding I1, to attract the armature I4. However, winding I8 is capable of holding armature I4 in attracted position. When both windings I1 and I8 are connected in parallel and both together in series with relay magnet coil 25, an armature (not shown) of the relay separates the normally closed pair of contacts B, thereby interrupting 'the ow of current from the battery to the ignition apparatus. This results in the prevention of the ignition of combustible mixture in the engine cylinder for a few cycles of operation. During this brief interval, the engine is not developing power. Therefore, no torque is being transmitted through the overdrive mechanism and there is no torque reaction between the sun gear II and the sun gear latch I2. Hence the latch solenoid magnet coils I1 and I8', though they be of relatively small electrical dimensions, are effective to produce the attraction of the solenoid armature I4 upwardly to lift the sun gear latch I2 out of engagement with the hub of the sun gear II. As stated before, this upward movement of the solenoid armature I4 causes the rod I5 to engage the blade 2 I,

separate the contact 20 from the contact I9.

However, current will continue to ilow through includes also a magnet coil 21 connected with the storage battery and with ground through a switch S which comprises a movable switch contact 30 cngageable with a stationary contact 28 connected with themagnet coil 21 and with a stationary contact 29 which is grounded.

Fig. 1 shows the overdrive mechanism in operating condition. As indicated in the first line of the chart of Fig. 2, the sun gear I I-is locked; the centrifugal latch 4 connects the parts 3 and 5; the solenoid latch I2 engages the hub of the sun gear II; the switch S is open; the contacts A of the relay assembly are open; and the contacts B are closed. The overdrive operation consists of the magnet coil I8 which is sulciently strong to maintain the armature I4 in the attracted position. The interruption of the flow of current through the solenoid magnet coil I1 reduces the total amount of current flowing through the relay magnet coil 25. The relay which includes this coil is so constructed that the contacts B will be opened only when current is flowing from the battery 26 through both magnet coils I1 and4 I8 of the latch solenoid; but, when current flows only through the solenoid magnet coil I8, the amount of current flowing through the 'relay magnet coil 25 will be insuilicient to maintain the contacts B open. As a result of this correlation between the relay, which includes contacts B and the magnet coil 25, and the latch solenoid, there will be a brief transition period during which the ignition is cut oil. This transition period is explained in the second line of the chart Fig, 2. This second line of Fig. 2 shows that the sun gear II is locked at the beginning of the transition period. The centrifugal latch 4 is still engaged. Thesolenoid latch is at engaged position at the beginning of the transition period and moves to disengaged position at the end of the transition period. 'I'he switch S remains closed; the contacts A remain closed, but the contacts B are opened during the transition period. During this transition period the ignition is cut oi for a time approximating .025 of a second. This interval oi.' .025 of a second represents approximately the time between the closing of the switch S and the retraction of the sun gear latch l2 from the hub of the sun gear and the opening of the contacts I9 and 20.

Immediately following the transition period during which the sun gear latch is disengaged, there follows the direct drive operation as indicated by the last line of the chart, Fig. 2. According to the last line of Fig. 2, the sun gear Il is unlocked so that it is free to rotate. The centrifugal latch 4 remains in position for connecting the parts 3 and 5. The solenoid latch I2 is now disengaged. The switch S remains closed; the contactsA remain closed; and the contacts B, which were open during the transition period are now closed due to the fact that the amount of current passing through the relay magnet coil 25 is only that which is permitted by the existence of the wires and connecting coil with the batteryv and also the resistance of the latch solenoid magnet coil I8. During direct drive operation, the transmission of power takes .place through the shaft I, splines 2, overrunning .clutch driving member 9, overrunning clutch power transmitting rollers I and overrunning clutch driven members 1 and the coupling member 8. When it is desired to resume operation of the overdrive mechanism, the car'driver merely releases the switch S whereupon conditions are restored to that shown in Fig. 1.

While the embodiment of the present invention as herein disclosed, constitutes a preferred ing the current source with the automobile engine ignition, said relay switch having a magnet coil i-n series with the current source and latch magnet windings for the purpose of opening the ignition circuit when the latch magnet operates to retract the latch vfrom the sun gear, and means responsive to the retractive movement of the latch for decreasing the amount of current owthe retractive movement of the latch causes the low resistance winding to be open-circuited thereby increasing the resistance of the circuit which includes the relay switch magnet coil.

3. A system of electrical control of automobile overdrives comprising the combination with an overdrive mechanism having a sunl gear and latch for restraining movement of the sun gear, of a. latch operating electromagnet, a current source, a switch for connecting the winding of the latch magnet with the current source, engine ignition apparatus operated by current from -the current source, means responsive to operation of said switch for disconnecting the current source from the ignition apparatus, and means responsive to retraction of the latch for rendering ineffective the means which disconnects the current source from the ignition apparatus.

form, it is to be understood that other forms might be adopted, all coming within the scope oi the claims which lfollow.

What is claimed is as follows:

1. A system of electrical control of automobile overdrives comprising the combination with an overdrive mechanism having a. sun gear and a latch for restraining movement of the sun gear, of a latch operating electromagnet, a current source. a switch for connecting the winding of 'the latch magnet with the current source. a normally closed, magnet opened relay switch for connect- 4. A system of electrical control of automobile overdrives comprising the combination with an overdrive mechanism having a sun gear and a latch for restraining movement of the sun gear,

of a latch operating electromagnet, a current source, a switch for connecting the winding of the latch magnet with the current source, engine ignition apparatus operated by current from the current source, a relay switch rendered 0perative in response to operation of the rst named switch for disconnecting the current source from the ignition apparatus, and means responsive to retraction of the latch for reducing the current in the magnet coil of the relay switch in order to render said relay switch ineiective to disconnect .the current source from the ignition apparatus. i

EDWARD M. CLAYTOR. 

